1. Field of the Invention
The present invention relates to a thin film magnetic head having a toroidal coil structure winding about a magnetic layer, and in particular relates to a thin film magnetic head capable of further simply connecting between first coil pieces and second coil pieces with small connection resistance and capable of improving the magnetization efficiency while suppressing the magnetic saturation.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 5-250636, which will be described below, discloses a toroidal thin film magnetic head in that coil pieces are toroidally wound about a magnetic layer constituting an inductive head (recording head). The sectional shape of this thin film magnetic head is copied on FIG. 33.
As shown in FIG. 33, on a substrate 2, first coil pieces 5 are formed under the magnetic layer 4 with an insulating layer 3 therebetween, and on the first coil pieces 5, an insulating layer 6 and the magnetic layer 4 are formed. An insulating layer 7 is formed along from on both sides of the magnetic layer 4 to the upper surface thereof. Along from the upper surface of the insulating layer 7 to the upper surfaces of the first coil pieces 5, second coil pieces 8 are formed with a through-hole 12 therebetween. The first coil pieces 5 and the second coil pieces 8 are electrically connected together in a connected state with connection portions 9. On the side of the connection portion 9, an insulating layer 10 is formed while an insulating layer 11 is formed along from the upper surface of the second coil pieces 8 to the upper surface of the insulating layer 7.
On the other hand, Japanese Unexamined Patent Application Publication No. 50-147916, No. 50-147917, and Japanese Unexamined Utility Model Registration Application Publication No. 61-132516 also disclose a toroidal thin film magnetic head having coil pieces toroidally wound about a magnetic layer constituting an inductive head (recording head). Also, in these thin film magnetic heads, first coil pieces formed under a magnetic layer and second coil pieces formed on the magnetic layer are electrically connected together in a contact state. In these thin film magnetic heads, a recess is formed on the surface of a lower core layer, and along from the surface of the lower core layer to the bottom surface of the recess, the first coil pieces are formed on the magnetic layer. The center region of the first coil pieces is formed along from the upper surface of the recess to the side thereof, and the side-ends of the first coil pieces are formed on the surface of the lower core layer. Therefore, the both side-ends of the first coil pieces are positioned above the center region. The both side-ends of the first coil pieces are electrically connected to the side-ends of the second coil pieces in a contact state.
However, in the thin film magnetic head 1 disclosed in Japanese Unexamined Patent Application Publication No. 5-250636, it is necessary for connecting the first coil pieces 5 to the second coil pieces 8 to form the through-hole 12 on the insulating layer 7. It is disclosed that the through-hole 12 is formed by etching; however, since it is difficult to form the through-holes 12 at precise positions and depths with a high degree of accuracy, there has been a problem that the connection between the first coil pieces 5 and the second coil pieces 8 becomes defective and the coil resistance is increased. That is, the positional displacement of the through-holes 12 and reduction in size of the through-hole 12 reduce contact areas between the first coil pieces 5 and the second coil pieces 8, and increase the electrical resistance. As a result, heat is liable to be produced in the vicinity of the connection portion 9, increasing the inside temperature of the thin film magnetic head. If the inside temperature of the thin film magnetic head is increased, a surface opposing a recording medium protrudes in front of the substrate (slider) because of the thermal expansion coefficient difference to the core layer and the insulating layer. As a result, the thin film magnetic head may collide on the recording medium so as to damage the thin film magnetic head and the recording medium.
There is also a problem that the first coil pieces are damaged during forming the through-holes.
In the thin film magnetic head 1 disclosed in Japanese Unexamined Patent Application Publication No. 5-250636, the second coil pieces 8 are connected to the first coil pieces 5 in a downward slanted state, and the film thickness of the slanted portion is reduced because the plating is difficult to be promoted therein. Thereby, this also produces problems of increase in electric resistance and of the thermal development.
In the thin film magnetic heads disclosed in Japanese Unexamined Patent Application Publication No. 50-147916, No. 50-147917, and Japanese Unexamined Utility Model Registration Application Publication No. 61-132516, since the lower core layer is provided with a recess formed thereon, the sectional area of the lower core layer is reduced, the magnetic saturation is facilitated.
Furthermore, in the thin film magnetic heads disclosed in Japanese Unexamined Patent Application Publication No. 50-147916, No. 50-145917, and Japanese Unexamined Utility Model Registration Application Publication No. 61-132516, in the same way as that in Japanese Unexamined Patent Application Publication No. 5-250636, the connection portion between the first coil pieces and the second coil pieces is provided with the through-hole. The first coil pieces and the second coil pieces are connected together via the through-holes, so that the electric resistance and thermal development are liable to increase in the vicinity of the connection portion between the first coil pieces and the second coil pieces because of faulty connection. Also, in the method for connecting the first coil pieces to the second coil pieces by forming through-holes, the first coil pieces may be damaged during the forming the through-holes.